TW201919746A - Filter element for wafer processing assembly - Google Patents

Abstract

Filter elements for gaseous fluid (e.g., air) filtration for wafer processing systems. The filter elements have a pleat ratio of no greater than 7, where the pleat ratio is the number of pleats per mean diameter of the filter. By having a pleat ratio no greater than 7, and in some implementations also greater than 5, the filter is optimized for wafer processing systems and methods. This pleat ratio optimizes the spacing between pleats, thus balancing filtration media area against effective area, such as what might be lost due to contaminant bridging.

Description

Filter element for wafer processing assembly

Filter elements have long been used to remove particulate material from fluid streams, which include gaseous fluid streams such as air. The design, configuration, and / or construction of the filter element will vary depending on the particular implementation and the performance of the filter element required.

The technology described herein relates to a filter element for filtering a gaseous fluid (eg, air) in a wafer processing system. The filter elements have a pleating ratio of not more than 7, where the pleating ratio is the number of pleated portions / average diameter of the filter.

One particular implementation described herein is a gaseous fluid filter element having an extension of a filter medium extending from a first end to a second end opposite the first end, the filter medium forming a circumferentially extending filter element. A plurality of pleated portions, the plurality of pleated portions defining an inner diameter and an outer diameter, wherein the filter element has a pleating ratio of no more than 7 and in other implementations no more than 6.5. In some implementations, the pleating ratio is at least 5.

Another specific implementation described herein is a wafer processing assembly having a filter element therein for filtering gaseous exhaust gas from a processing chamber upstream of the pump. The filter element includes an extended portion of a filter medium extending from a first end to a second end opposite the first end, the filter medium forming a plurality of pleated portions extending circumferentially around the filter element, the plurality of pleated portions defining Inner diameter and outer diameter, wherein the filter element has a pleating ratio of not more than 7.

Another specific implementation described herein is a method for cleaning exhaust in a wafer processing assembly. The method includes passing an atmosphere from a processing chamber of a wafer processing assembly through a filter element having a pleating ratio of no more than 7 to form filtered exhaust, and pumping the filtered exhaust.

These and various other implementations, features, and advantages will be apparent from reading the following detailed description.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the embodiments. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

This specification relates to fluid filters for wafer processing assemblies and / or systems, specifically gas (such as air) filters. The wafer processing system may be, for example, a chemical vapor deposition (CVD) system, a metal organic chemical vapor deposition (MOCVD) system, an ion beam deposition system, an ion beam sputtering system, a chemical etching system, Ion milling system, physical vapor deposition (PVD) system, diamond-like carbon (DLC) deposition system, or other processing systems.

In the following description, reference is made to the accompanying drawings, which form a part of the description and are shown in detail by way of illustration. This description provides additional implementations. It should be understood that other implementations are covered and can be made without departing from the scope or spirit of the invention. Therefore, the following detailed description should not be interpreted in a limiting sense. Although the invention is not limited thereto, an understanding of various aspects of the invention will be obtained by discussing the examples provided below.

As used herein, the singular forms "a" and "the" cover embodiments having plural referents unless the content clearly dictates otherwise. Unless the content clearly specifies otherwise, as used in this specification and the scope of the accompanying patent application, the term "or" is generally used in its sense to include "and / or".

Space-related terms, including but not limited to "lower", "upper", "bottom", "below", "above", "top", etc. (if used herein) are used to make the description easy to depict the space between elements relationship. Such spatially related terms encompass different orientations of the device in addition to the drawings and the specific orientations depicted herein. For example, if a structure depicted in a drawing is reversed or turned over, portions previously described as being under or underneath other elements would then be above / over them.

In some examples, reference numerals in the drawings may have associated sub-tags composed of capital letters to represent one of a plurality of similar components. When a reference number is referred to without specifying a sub-tag, the reference number refers to all such multiple similar components.

FIG. 1 illustrates a wafer processing system 100, such as a CVD system, in an extremely basic manner. The specific system 100 is not critical to the filter of the present invention, but is provided as a general-purpose wafer processing system in which the filter of the present invention can be incorporated. The specific system 100 shows only certain parts and is generally not shown with a special design; it should be understood that actual CVD systems or other wafer processing systems have significantly more features present.

The wafer processing system 100 has a chamber 102 formed by at least a first portion 104 and a second portion 106, and a wafer (not illustrated) is disposed in the chamber 102 for processing. In a specific implementation, the chamber 102 has a cylindrical volume formed by a cylindrical first portion 104 mating with the annular second portion 106 with a seal (not shown) in between. The processing in the chamber 102 may be, for example, used to deposit a metal oxide film on a wafer. The display cover 108 is above the second portion 106. The rendering center hub 110 extends through the cover 108 to the second portion 106.

A substrate support 112 is present within the chamber 102 for placing a wafer thereon or therein during processing. Although not shown, the system 100 will include an entrance into the chamber 102 for moving wafers into and out of the chamber 102.

Depending on the particular processing system, the system 100 may also include a suction source 114 for drawing a vacuum on the chamber 102, and gas feed ports 116, 118 for supplying (e.g., reactive) gas to the chamber 102. The system 100 may also include an exhaust port 120 to maintain the desired atmosphere quality in the chamber 102 and / or to maintain circulation within the chamber 102. A gaseous atmosphere (eg, air) in the chamber 102 exits the chamber 102 via the exhaust port 120 and is discharged to the outside atmosphere in some implementations. However, in order to prevent the processing material from escaping and polluting the external atmosphere, at least one filter element 125 is in fluid communication with the chamber 102 and the exhaust port 120 and is located therebetween. The filter element 125 is configured to remove particulate (solid) pollutants therefrom at least before the exhaust stream is discharged. In this particular illustration, the filter element 125 is located in a separation chamber 122 fluidly connected to the chamber 102, but in other implementations, the filter element 125 may be physically disposed in the chamber 102. After the exhaust flow has been cleaned by the filter element 125, the exhaust flow may be discharged.

In some implementations, the extraction source 114 and the exhaust port 120 are combined so that the atmosphere removed from the chamber 102 to obtain a vacuum is discharged to the atmosphere.

In either case, the filter element 125 is disposed between the interior of the chamber 102 and a pump (such as a vacuum pump) for removing air from the chamber (the pump is not shown in FIG. 1). Having a filter element 125 upstream of the pump, in addition to removing pollutants before discharging, also protects the pump from contamination and increases the pump's operating life.

FIG. 2 illustrates an example filter element 200 for removing contaminants from a gaseous fluid stream. The filter element 200 has a filter medium formed into a plurality of pleated portions 202, and each of the pleated portions 202 has a tip 204 and a base 206. Each pleated portion 202 generally extends from one end to the other end of the filter element 200 such that the pleated portion 202 extends the entire length of the filter element 200. The filter element 200 has an annular cross-section as shown in FIG. 2 having an inner diameter D _I defined by the base 206 of the pleated portion 202 and an outer diameter D _O defined by the tip 204 of the pleated portion 202. The filter element 200 may be a cylinder, a conical cylinder (a truncated cone), a cone, or have an irregular shape having an annular cross section. Filter elements with a circular cross section are often referred to as "tubular" filter elements.

The filter element 200 has a pleating ratio that provides a maximum useful cross-sectional area for a given volume of the filter element 200. The pleating ratio is defined as the number of pleated portions / average diameter of the filter; that is, the number of pleated portions divided by (D _I + D _O ) / 2. As an example, a filter element having 102 pleated portions (the height of the pleated portion is 2.8125 inches) with a D _I of 9.0 inches and a D _O of 14.625 inches has a pleated ratio of 8.63, and the same size with 64 pleated portions The pleating ratio of the filter was 5.42. As another example, having a D 70 pleats-like portion (pleated part of the height of 1.875 inches) to 6.0 inches _I, D _O 9.75 inch pleats of the pleated filter element ratio of 8.89, and having a pleated portion 48 The pleating ratio of filters of the same size is 6.10. Another example has a filter element with a pleating ratio of 8.83, whose pleating ratio is reduced to a ratio of 5.42.

The filter medium may be, for example, paper, other cellulosic materials, synthetic materials, or any combination thereof. Filter media can be perforated pads or fibrous pads or meshes formed from polymeric or cellulose fibers. Filter media can be processed in any number of ways to increase its efficiency in removing small particles; for example, electrostatically treated media can be used, or cellulose or synthetic media, or a combination thereof, having a size of micrometers or submicrometers (fibers Diameter) or one or more layers of fine-grained fibers, or other types of media known to those skilled in the art.

A gaseous atmosphere (such as air) flows through the filter medium and the filter element 200 passes radially through the pleated medium in this implementation, identifying as an air flow path 210. Particles that are too large to pass through the filter medium are captured by the medium on the surface of the pleated portion 202. The filtered air exits from the internal volume of the filter element 200.

Pleated filter elements, such as filter element 200, can be used to filter particulate contaminants from an exhaust stream from a wafer processing system (e.g., MOCVD). The filter element 200 may be designed based on the type of contaminants to be removed from the filtered fluid (eg, gas) stream. Example particulate contaminants in the exhaust stream of a wafer processing system (eg, MOCVD) are GaN dust, a by-product of wafer processing. Other contaminants that can be removed from the gaseous fluid stream by the filter element 200 include dust, dirt, pollen, metal wafers and / or shavings, and the like. Some particles may cause double damage to the operation of the wafer processing system due to the physical particles and molecular structure of the particles.

FIG. 3 illustrates an example orientation of the filter element construction 300. In a particular implementation, three separate filter elements 300A, 300B, 300C are placed end-to-end. The filter element structure 300 has a first end 302 and a second end 304; in this particular implementation, the first end 302 is an "open" end and the second end 304 is a closed end. Although the first end 302 is referred to as the "open" end, the entire surface of the end 302 may not be open, but only a sufficient amount to allow air flow through the end 302. For example, the open end 302 may have a central orifice. A filter medium 306 forming a plurality of pleated portions 308 extends from the first end 302 to the second end 304. The filter element structure 300 has an internal volume defined by a separate filter element 300, a first end 302, and a second end 304.

When placed in a wafer processing assembly (eg, assembly 100 of FIG. 1), the filter structure 300 may be placed in a horizontal orientation, as shown in FIG. 3 and schematically shown in FIG. 1. A gaseous fluid (such as air) enters the internal volume by passing through the medium into the internal volume, and exits the internal volume via the open end 302. The incoming air and outgoing air shown as an air flow path 310 are shown in FIG. 3; the flow path 310 passes radially through the filter medium 306 into the internal volume of the filter and flows out through the open end 302.

According to the present invention, the filter elements 200, 300 have a pleating ratio of not more than 7. As explained above with reference to FIG. 2, the pleating ratio is the number of pleated portions / average diameter of the filter, or the number of pleated portions divided by (D _I + D _O ) / 2. Some examples of pleated filter configurations and pleated ratios are also provided above with reference to FIG. 2. In some implementations, the pleating ratio is not greater than 6.9 or 6.8 or 6.75 or 6.7 or 6.6 or 6.5 or 6.4 or 6.3 or 6.25 or 6.2 or 6.1 or even not greater than 6. In other implementations, the pleating ratio is not greater than 5.9 or 5.8 or 5.75 or 5.7 or 5.6 or 5.5 or 5.4 or 5.3 or 5.2 or 5.25 or 5.1 or even not more than 5. Generally speaking, the pleating ratio is at least 2 and at least 2.5 in some implementations, at least 3 in other implementations, at least 3.5 in other implementations, and at least 4 or at least 5 in other implementations. In some implementations, the pleat ratio is between 5 and 6.5, and in other implementations between 5 and 6.

The pleated portion in the filter element increases the filtering area compared to a non-pleated filter, and the pleated portion further improves the filtering ability and therefore the life. However, excessive pleated portions actually reduce filter life despite increasing filter media area. Too few pleated portions (close to simple cylinders in extreme cases) will have extremely small area and lifetime. The pleating ratio defines this sweet spot that maximizes the life of the filter.

The pleating ratio quantifies the optimal (or near optimal) useful filter cross-sectional area for a given volume. The pleating ratio can be adjusted by adjusting any or all of the number of pleated portions, the inner diameter (D _I ), and the outer diameter (D _O ). To reduce the pleating ratio, the number of pleated portions can be reduced, the inner diameter (D _I ) can be increased, and / or the outer diameter (D _O ) can be increased. Because the filter element in the system (such as the filter element 125 in the system 100) has a certain shape factor (such as volume, length, width, etc.), the number of pleated portions can be easily adjusted to affect the pleating ratio. The pleating ratio required for a certain filter can vary based on the type of material being filtered, the gaseous fluid being filtered, and the type of filtering media used to some extent.

Depending on the specific application, the average diameter of the filter (ie (D _I + D _O ) / 2) is at least 6 inches, and in some implementations at least 7 inches. Other suitable examples of average diameters are 8 inches, 9 inches, 10 inches, 11 inches, and 12 inches. The average diameter of the filter element is close to the two-dimensional filtering area of the filter, which is different from the height of the pleated portion, which does not occupy the size of the filter (inner diameter (D _I ) and outer diameter (D _O )). This slight difference between the average diameter and the height of the pleated portion is one of the keys to the pleated ratio. The pleated ratio is a figure of merit unique to the filter that incorporates the area of the filter and the pitch of the pleated portion.

The difference between the inner diameter and the outer diameter may be at least 1 inch, in some implementations at least 2 inches, and in other implementations at least 3 inches. Too short pleated portions cannot provide sufficient surface area of the filter medium, thereby reducing the effectiveness of the filter element.

The difference between the inner and outer diameters is no more than 6 inches to 9 inches, and in some implementations no more than about 4 inches. Excessively high pleated portions may tend to sink or fold, reducing the effectiveness of the filter element. In addition, the height of the larger pleated portion increases the outer diameter D _O , which directly affects the shape factor of the filter element, which is related to the volume that can be used to receive the filter element in the system, the packaging and storage of the filter element, and the like.

In some implementations, a permeable support (such as a screen) may be present on the outer and / or inner surface of the pleated portion (especially for larger pleated portions) to support the pleated portion and / or protect the medium.

The number of pleated sections will largely depend on the circumference of the filter (or the outer diameter D _{O of the} filter), but will generally be at least 30 pleated sections or at least 40 pleated sections or at least 50 pleated Portions, and / or no more than about 90 pleated portions or no more than 80 pleated portions. Other examples include 35-75 pleated portions, 40-80 pleated portions, 40-60 pleated portions, and 45-65 pleated portions.

The number of pleats, especially the lower limit, depends on the gaseous fluid flow and the allowable pressure drop across the filter element. The filter element must have sufficient area to allow the required gas to pass through it over a period of time at a maximum pressure drop that is application specific and determined by analyzing the exhaust flow and the amount of particles captured. Having more pleated portions and therefore a larger media area extends the time between filter replacements, however, if the pleating ratio is exceeded, the additional area may actually shorten the life of the filter element.

By reducing the number of pleated portions while maintaining the same average diameter, the total medium area is reduced. However, although the total medium area is reduced, the effective medium area is increased.

When smaller media surface areas are used for the same amount of fluid (eg, gas) material flow, particulate contaminants have a smaller area to capture them, and therefore cause more contaminants to accumulate on the media. It was unexpectedly found that the pressure drop (DP) in the filter was reduced compared to a filter having a pleating ratio of not more than 7 compared to a filter having the same average diameter and more number of pleated portions (that is, a higher pleating ratio). Instead of increasing the pressure drop (for example, the filter element "clogs" and becomes slower). Low pressure drop or slower pressure drop increase rate to extend the efficiency and productivity of the filter.

The pressure drop (DP) in the filter can be used to measure the performance of the filter and trigger the maintenance cycle of the protected equipment (such as MOCVD or other wafer processing systems). As the filter element captures contaminants, the flow through the filter element and therefore through the entire system gradually decreases as the pressure drop in the filter increases. As the pressure drop increases, the pump must run with more power to move the same volume of air. For a typical filter element configuration, reducing the level of filtration (e.g., increasing the size and / or number of particles passing through the filter by changing the medium or its treatment) can maintain low DP for a longer period of time, providing Long filter life and maintenance intervals, but in turn will significantly reduce vacuum pump life due to the size and / or amount of particles passing through the filter to the pump. Higher filtration levels can be easily achieved to provide better protection for the pump, but require more frequent filter changes and additional system maintenance. Therefore, it is desirable to reduce DP without sacrificing the level of filtration. It has been unexpectedly found that having a pleating ratio of no more than 7 reduces the increase in pressure drop (DP) in the filter without the need to reduce the level of filtration.

In fact, by allowing the use of finer media that can remove smaller size particles from the gaseous fluid stream and / or by extending the life of the filter element, it was unexpectedly found that having a pleating ratio of no more than 7 not only reduces the filter The rate of increase in medium pressure drop (DP) increases the level of filtration available. The applicant considers this to be a direct effect of the "pleating ratio" effect; using the optimal pleating ratio, the filter element has a more effective medium available due to the optimal spacing between the pleated portions. During the filtration process, all available area of the filter medium is used, so that the pressure drop rises at a slower rate than when the distance between adjacent pleated portions is small. This allows more filtration due to the increased effective filtration area, such as removal of smaller particles and / or longer filtration life.

Because the pleated specific pressure drop does not increase more than 7 and the effective medium area increases slowly, thinner filter media can be used; filter elements with a ratio higher than 7 will load too fast and reach DP too quickly. The use of the same filter media in filter elements with a pleating ratio of no more than 7 allows the filter elements to load more slowly while providing better protection for downstream elements.

Although not limited by this theory, the applicant believes that one or both of the reduction in pressure drop (DP) in the filter and the increase in filtration, the decrease in particle size or the extension of the filter life are attributed between the pleated portions Optimized spacing. In some implementations, this can be attributed to the extra volume that receives and holds particulate contamination between adjacent pleated portions. In addition, the larger spacing between the pleated portions reduces the occurrence of contaminant bridging between adjacent pleated portions. Suppressing contaminant bridging increases the area of available filter media (effective media area) and extends filter life, thereby providing a slower increase in pressure drop.

The applicant has found that for wafer deposition systems (eg, CVD, MOCVD), for currently used tools, systems, and methods, a filter element having a pleating ratio of no more than 7 is optimal. However, based on the fluid being filtered, the contaminants removed from it, the fluid flow rate, etc., there is an optimal pleat ratio for each application. Applicants have found that filters can be specifically designed to meet the ratios determined by the application.

As explained above, having a pleating ratio of no greater than 7 (in some implementations no greater than 6.5, or no greater than 6.2, or no greater than 6 etc.) results in a unique ability to increase long filter life and high filtration levels. Increased filtration levels lead to longer pump life and lower pump maintenance costs. Optimization also allows extended maintenance intervals (such as filter life and related parts, chamber cleaning, etc.) consistent with the use of high filtration levels (such as passing smaller sized particles and fewer particles). This unique combination of high filtration and long maintenance cycles reduces the total cost of ownership of the wafer processing system, as maintenance cycles are an important part of the total cost of ownership. Not only does the maintenance activity itself have costs (such as the cost of new filter elements, other seals or equipment that may have to be replaced (such as pumps), the cost of repair technicians, lost productivity due to systems being shut down for maintenance), but also every maintenance Reactors or other wafer processing systems. After maintenance, the system does not return to full production capacity until several runs. All or part of the previous runs were waste materials, increasing material, time, productivity, etc.

By extending the life of the filter element, the number and frequency of maintenance cycles are reduced. In addition, the long life of the filter element results in a reduction in the number of filter elements that are being used and that have been placed over the same period, as well as parts related to filter element replacement. Compared to lower filtration levels, the life of the vacuum pump is also protected and extended, further improving the cost of ownership.

The following compares filter No. 1 (a filter element with 6.0 inches in D _{I and} 9.75 inches in D _O with 70 pleated portions, so a pleated ratio of 8.89) and filter No. 2 (with 48 pleated portions and Therefore, the pleating ratio is 6.10.

Each of the No. 1 and No. 2 filter elements is installed in a MOCVD wafer processing system. Measure and record the pressure drop across the filter after a processing run. After completing "X" runs, and measuring and recording the pressure drop in the filter after "X" processing runs. After these "X" runs, the reactor was cleaned without replacing the filter element. After completing "Y" additional runs, and measuring and recording the pressure drop in the filter after "Y" processing runs.

In general, based on the operation using different size filter elements under various conditions, it was found that filters with a pleating ratio greater than 7 (e.g. 8.89) have a typical life of less than 125 runs and provide a filtration level of 25 microns, Filters of the same size and shape but with fewer pleated portions to provide a pleated ratio of no more than 7 (eg 6.10) have a life of more than 240 runs and provide a filtration level of 5 microns.

In summary, the present invention provides a filter element for removing particulate contaminants from a gaseous fluid, such as air, which has a pleating ratio of no greater than 7 and in some implementations greater than 2, 3, or 4.

The above specification and examples provide a complete description of the structure, features, and uses of the exemplary implementation of the invention. Since many implementations of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the scope of the patent applications appended below. In addition, the structural features of different implementations can be combined in another implementation without departing from the scope of the patent application.

100‧‧‧ Wafer Processing System / System / Assembly

102‧‧‧ Chamber

104‧‧‧ Part I

106‧‧‧ Part Two

108‧‧‧ Cover

110‧‧‧Center Hub

112‧‧‧ substrate support

114‧‧‧Exhaust source

116‧‧‧Gas inlet

118‧‧‧Gas inlet

120‧‧‧ exhaust port

122‧‧‧ separation chamber

125‧‧‧filter element

200‧‧‧Filter element

202‧‧‧ Pleated section

204‧‧‧ Tip

206‧‧‧ substrate

210‧‧‧Air flow path

300‧‧‧Filter element structure

300A‧‧‧Filter element

300B‧‧‧Filter element

300C‧‧‧Filter element

302‧‧‧ the first end

304‧‧‧Second End

310‧‧‧Air flow path

D _I ‧‧‧ Inner diameter

D _O ‧‧‧ Outer diameter

FIG. 1 is a schematic cross-sectional side view of a general wafer processing assembly.

Fig. 2 is a schematic cross-sectional top view of a filter element.

Figure 3 is a side perspective view of a filter element configuration.

Claims (14)

A gaseous fluid filter element for a wafer processing system, the filter element includes an extension portion of a filter medium extending from a first end to a second end opposite to the first end, the filter medium forming a circumference surrounding the filter element A plurality of pleated portions extending on the ground, the plurality of pleated portions defining an inner diameter and an outer diameter, wherein the filter element has a pleating ratio of not more than 7. A filter element as claimed in claim 1 having a radially inward gaseous fluid flow through the filter medium. The filter element of claim 1, wherein the pleating ratio is not greater than 6.5. The filter element of claim 1, wherein the pleating ratio is not greater than 6. The filter element of claim 1, wherein the pleating ratio is at least 5. The filter element of claim 1, wherein the pleating ratio is 5 to 6. A wafer processing assembly having a filter element therein for filtering gaseous exhaust gas from a processing chamber upstream of a pump, the filter element including a first end extending to a second end opposite to the first end An extended portion of the filter medium, the filter medium forming a plurality of pleated portions extending circumferentially around the filter element, the plurality of pleated portions defining an inner diameter and an outer diameter, wherein the filter element has pleats of no more than 7 ratio. As in the wafer processing assembly of claim 7, wherein the filter element is oriented at a position horizontal to a radial inward gaseous flow path passing through the filter element. For example, the wafer processing assembly of item 7, wherein the pleat ratio is not greater than 6.5. For example, the wafer processing assembly of item 7, wherein the pleat ratio is not greater than 6. For example, the wafer processing assembly of claim 7, wherein the pleat ratio is at least 5. If the wafer processing assembly of item 7 is requested, this assembly becomes the MOCVD assembly. A method for cleaning exhaust gas from a wafer processing assembly, comprising: passing an atmosphere from a processing chamber of the wafer processing assembly through a filter element having a pleating ratio of not more than 7 to form a filtered exhaust gas, And pump the filtered exhaust. The method of claim 13, further comprising pumping the filtered exhaust from the wafer processing assembly.